Persistent infection of mink with Aleutian mink disease parvovirus (ADV) causes disturbances of immune regulation, including polyclonal hypergammaglobulinemia, plasmacytosis, immune complex disease, interstitial and glomerulonephritis and exceedingly high levels of anti- ADV antibodies. The spectrum of findings resembles those associated with a Th2 pattern of cytokine responses and previous work implicates a possible role for IL-6. The scope of this project is to elucidate mechanisms by which ADV infection results in this unusual disorder. The U937 cells used previously in antibody-dependent enhancement (ADE) of ADV infection were found to be mixture of 2 monocytic cell lines, >90% K562 and <10% U937. Experiments with pure cell populations indicated that K562, but not U937 cells were susceptible to ADV via ADE. Infection was via the Fc gamma RII receptor. IL-6 was elaborated by K562 cells in response to ADV infection. In order to evaluate the role of selected cytokines in the immune disorder associated with ADV infections, RT-PCR was done on mRNA from tissues from infected mink. Degenerate primers for IL-4, IL-5, IL-10, IL- 12 p35 and IL-12 p40 were based on consensus sequences from human, mouse, cat, rat, cow and pig. Appropriate sized PCR products were obtained and have been cloned. DNA sequencing is currently being done. In order to identify early target cells for viral replication, mink were infected both intranasally (IN) and intraperitoneally (IP) with ADV. Progressive disease develops by either route, but progression seems slower after IN infection. Earliest evidence of ADV DNA was localized by PCR to draining lymphoid tissues. In order to compare the subcellular localization of ADV proteins and nucleic acids in permissive and restricted infection, specific antisera for nonstructural (NS) and capsid proteins have been prepared and conjugated to fluorochromes. Asymmetric PCR has been used to develop fluoresceinated strand specific probes for fluorescence in situ hybridization (FISH). Preliminary work on synchronized cells with multi- channel epifluorescence and confocal microscopy suggests that NS1 and NS2 co-localize, but that NS and capsid proteins are spatially segregated within the nucleus of permissively infected cells.